Magnetoencephalography(MEG) allows for noninvasively localizing and monitoring brain activity in real time. The aim of this protocol is to use MEG for presurgical localization of brain areas especially in patients with brain tumors and epilepsy. In all patients, the primary sensory and motor areas of cortex, and in epilepsy patients, brain regions which exihibit epileptiform spike activity will be identified. The MEG data will be superimposed upon the patient's magnetic resonance imaging (MRI)scan, showing structural brain areas, and correlating MEG activity with brain structure. Presurgical mapping of this type has proven valuable for neurosurgeons by indicating which functional brain areas are implicated or not implicated in the pathology for which surgery is required, thus providing benefits to most patients.